OTTAWA -- Canada's minority Conservative government tried to boost its fragile grip on power Monday but suffered a rebuff when an opposition party said Ottawa was not being serious enough about fighting climate change.

Prime Minister Stephen Harper needs opposition support in Parliament to pass draft legislation to tackle the environment, a topic that polls show is of most concern to Canadians.

Critics blasted the bill -- which did not mention Canada's commitment to cut emissions under the Kyoto protocol -- when it was unveiled last year. Under pressure, Harper agreed to send it to a parliamentary committee so it could be strengthened .

Behind the scenes, top Conservatives are sounding out the opposition as to what kind of changes they want.

Bernard Bigras, environment spokesman for the opposition Bloc Quebecois, met with Environment Minister John Baird on Monday to insist the amended bill include a commitment to meet Canada's Kyoto commitments.

"It was a very disappointing meeting," said Bigras, telling Reuters that Baird did not seem to want to even discuss Kyoto.

"We'll put forward amendments and will hope the government comes down on the side of Kyoto. If not, we'll be forced to vote against the bill," he said. Harper says Canada has no chance of meeting its Kyoto commitments.

The government would not be brought down if Parliament rejected the bill but it would nevertheless embarrass Harper on a topic where he is vulnerable.

Baird said he was committed to "beefing up" the bill but gave no details. Asked whether he felt bound to Canada's Kyoto targets, he said Ottawa "felt bound to take every reasonable action we can take to improve our environment".

The Conservatives usually have little time for the Bloc, which wants independence for Quebec. The environment is a key issue in Quebec, where Harper has to win more seats in the next election to stand a chance of gaining a majority.

Harper also has to focus on how he can persuade Parliament to pass his annual budget, which is expected in March. He needs the support of at least one opposition party, and if the budget is defeated, the government will fall, triggering an election.

Polls show the Conservatives are tied with the opposition Liberals and that no party would gain a majority of seats if a federal vote were held now.

"What would be the point of an election, especially if it would just result in another minority anyway?" Harper told the Canadian Press news agency.

Liberal leader Stephane Dion also says he does not want an election and last week said he might back the budget.

But ties between the two parties soured on Monday after the Conservatives unveiled three advertisements attacking Dion, who was elected Liberal leader in December after promising to tackle climate change and to cut greenhouse gas emissions.

Harper says Dion is a hypocrite, given that emissions soared when the Liberals were in power from 1993 to 2006. One ad shows Dion spluttering "This is not fair" when an opponent in the Liberal leadership race points out the party's record.

"We decided to let the Liberals speak for themselves. I think Canadians will be surprised by what they hear from a man who wants to be prime minister," said senior Conservative legislator Jason Kenney.

Dion told reporters he was not worried by the ad campaign, saying: "It insults the intelligence of Canadians."